<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    html, body {
      height: 100%;
    }
    #app {
      height: 100%;
      display: flex;
      flex-direction: column;
    }

    header {
      width: 100%;
      height: 60px;
      background-color: aquamarine;
    }

    nav {
      width: 100%;
      height: 50px;
      background-color: lightcoral;
    }

    main {
      width: 100%;
      flex: 1;
      background-color: bisque;
    }

    footer {
      width: 100%;
      height: 60px;
      background-color: lightblue;
      display: flex;
    }

    section {
      height: 100%;
      flex: 1;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
    }
  </style>
</head>
<body>
  <div id="app">
    <header>header</header>
    <nav>nav</nav>
    <main>main</main>
    <footer>
      <section>
        <span>🏀</span>
        <p>首页</p>
      </section>
      <section>
        <span>⚽</span>
        <p>首页2</p>
      </section>
      <section>
        <span>🏐</span>
        <p>首页3</p>
      </section>
      <section>
        <span>🏓</span>
        <p>首页4</p>
      </section>
    </footer>
  </div>
</body>
</html>